A Moderate Wetting and Drying Regime Combined with Appropriate Nitrogen Application Increases Grain Yield and Nitrogen Use Efficiency in Rice
, Junfei Gu 1,2, Kuanyu Zhu 1,2,*, Jianhua Zhang 3,4 and Jianchang Yang 1,2Round 1
Reviewer 1 Report
This manuscript presents the detailed results of a field experiments in which the interaction between irrigation regime and N fertilization in rice yield and N use efficiency was examined. The results are interesting and the conclusions are supported by the results. I have only two main comments and a few minor specific comments:
Main comments:
1. Authors indicate that there are findings in the literature about the interaction between irrigation regime and N fertilization (both positive and negative responses), but they do not much discuss the possible underlying causes of these differences. Also, they do not critical reflect on the experimental design of their study; they included only two irrigation and only three N fertilization treatments, which is at the lower limit of what is possible to identify interactions. Also, there N treatments differed greatly in N application rate (difference between treatments was 120 kg); as a results the study did not allow to identify the optimal N application rate. The same applies to the irrigation regime; authors could have included more variations (more treatments) in irrigation. Including more treatments would have allowed to shed more light on the variable results so far on the interactions between irrigation regime and N fertilization.
2. Changing the irrigation regime is done to increase water use efficiency, resources use efficiency. However, authors do not discuss this issue. I suggests authors to include a discussion on the effect of irrigation regime on water use efficiency in rice production.
Minor/specific comments:
L96: how was the urea applied, through deep placement? What measures were used to prevent ammonia volatilization?
L110: is this a realistic situation for the AWMD regime?
L173: please report only statistically significant results (and not non-significant results)
L177: is that true? I which year? Were overall results statistically significant?
There are a few typing errors and misspellings, which can by addressed during the technical editing
Author Response
Reviewer(s)' Comments to Author:
Reviewer: 1
This manuscript presents the detailed results of a field experiments in which the interaction between irrigation regime and N fertilization in rice yield and N use efficiency was examined. The results are interesting and the conclusions are supported by the results. I have only two main comments and a few minor specific comments:
Main comments:
- Authors indicate that there are findings in the literature about the interaction between irrigation regime and N fertilization (both positive and negative responses), but they do not much discuss the possible underlying causes of these differences. Also, they do not critical reflect on the experimental design of their study; they included only two irrigation and only three N fertilization treatments, which is at the lower limit of what is possible to identify interactions. Also, there N treatments differed greatly in N application rate (difference between treatments was 120 kg); as a results the study did not allow to identify the optimal N application rate. The same applies to the irrigation regime; authors could have included more variations (more treatments) in irrigation. Including more treatments would have allowed to shed more light on the variable results so far on the interactions between irrigation regime and N fertilization.
Response: Thanks for the suggestions. We have discussed the possible underlying reasons of the differences involved in positive and negative responses caused by irrigation regimes and N application rates in lines 432-453 of the revised manuscript: “In addition, in the present study, the interaction between water and nitrogen led to both positive and negative effects on plant traits, particularly when comparing CF and AWMD. There are reports indicating that ammonium-N tends to be more readily retained when the paddy field is supplemented with CF [47,48]. Such an irrigation regime greatly facilitates the efficient and rapid uptake of nitrogen by the rice roots, which, traditionally, is highly advantageous for rice growth and development, such as more tiller number and larger LAI [49, 50]. In contrast, these parameters were all decreased in the AWMD regime (Figures 3 and 4). Fundamentally, it can be attributed to the fact that plant nutrients rely on water as a vehicle for transportation [51]. However, the implementation of AWMD, which significantly reduces water irrigation, consequently limits the vegetative growth [32,37,52]. On the other hand, although AWMD showed a disadvantage in quantitative changes of rice development, it induces qualitative changes within the plants compared to CF, especially of root and shoot activities (Figures 6 and 7). There are observations indicating an increase in nitrate-N content under the AWD regime, while reports suggest that nitrate-N induces the synthesis of root-derived cytokinins [37, 53]. Moreover, our previous work has demonstrated that root-derived cytokinins can improve both root and shoot activities, such as ROA and photosynthesis [54]. Therefore, we speculate that the qualitative changes within rice plants may be activated by root-derived cytokinins through the increase in nitrate-N content in the AWMD regime. However, further investigation is needed to confirm whether AWMD regulates root-derived cytokinins and promotes plant physiological performance.”
We also have reflected on the limitations of the experimental design and discussed it in line 455-463 of the revised manuscript (Discussion section): “Although this study has elucidated the interactive effects of water and nitrogen on grain yield, NUE and WUE in rice, it has been reported that the appropriate nitrogen application rates for attaining a desired grain yield may vary depending on soil moisture conditions, while the optimal soil moisture conditions may differ with different nitrogen application rates [55]. The irrigation regimes and nitrogen rates employed in the present study were relatively limited, thus precluding the determination of the optimal water-nitrogen combination that synergistically enhances grain yield and resource use efficiency. Therefore, further investigations are needed to explore the optimal water-nitrogen coupling model for improving rice grain yield and resource use efficiency by incorporating a broader range of water and nitrogen treatments.”
- Changing the irrigation regime is done to increase water use efficiency, resources use efficiency. However, authors do not discuss this issue. I suggests authors to include a discussion on the effect of irrigation regime on water use efficiency in rice production.
Response: Thanks for the suggestions. We have included the data on water use efficiency (WUE) in the Results section (line 220-225) and analyzed the underlying reasons in the Discussion section (line 404-419): “Meanwhile, the key to enhance crop water use efficiency (WUE) lies in harnessing the biological potential, thereby improving crop yields with limited water inputs [44]. We observed that AWMD significantly reduced irrigation water and improved WUE (Figure 2), indicating that AWMD unleashes the maximum biological potential of rice plants. However, the underlying reasons for this phenomenon remain unclear. Previous research suggests that a substantial reduction in transpiration can be achieved without compromising photosynthesis by appropriately reducing stomatal conductance [44]. It is also widely believed that AWMD can moderately increase the abscisic acid (ABA) level in rice plants, thereby properly decreasing stomatal conductance [45, 46]. In summary, these processes can reduce transpirational water loss while promoting matter production and remobilization. Interestingly, in the present study, AWMD exhibited higher photosynthesis and NSC remobilization compared to CF, indicating a greater potential for efficient matter production enabled by AWMD, possibly through the ABA pathway, and ultimately leading to an improved WUE. Investigation involving in ABA is warranted in the future.”
Minor/specific comments:
L96: how was the urea applied, through deep placement? What measures were used to prevent ammonia volatilization?
Response: The urea was applied using the broadcasting method, and mechanical deep plowing was conducted in the paddy field to mitigate ammonia volatilization. We have illustrated it in the M&M section (line 101-102).
L110: is this a realistic situation for the AWMD regime?
Response: It is a realistic situation. Tensiometers serve as a supplementary tool to validate the accuracy of SWP measurements and mutually validate the SWP monitoring system, ensuring more precise control of field soil water potential.
L173: please report only statistically significant results (and not non-significant results)
Response: Thanks for the suggestion. We have included the F values analysis in the Results section (line 183-187).
L177: is that true? In which year? Were overall results statistically significant?
Response: It’s true. The data in 2021 and 2022 showed a similar trend, and most of the data from the two-year experiment showed significant differences (Table S1). However, for the sake of clarity and conciseness in the Results section, we described the data as pooled across the two years in Results section.
There are a few typing errors and misspellings, which can by addressed during the technical editing
Response: Thanks for the kind suggestion. We have reviewed the entire document for spelling errors and corrected any incorrect spellings.
Reviewer 2 Report
Line 142: after "dry weight" I believe there is a period, not a comma.
For better visibility, images 1-7 should be larger, if the number of pages allows.
In the Conclusion section, I ask the authors to emphasize that the conclusions drawn refer to the researched cultivar.
Author Response
Comments to the Author
Line 142: after "dry weight" I believe there is a period, not a comma.
Response: Thanks for the suggestion. We have corrected it.
For better visibility, images 1-7 should be larger, if the number of pages allows.
Response: Thanks for the suggestion. We have enlarged and replaced the images with high-resolution ones.
In the Conclusion section, I ask the authors to emphasize that the conclusions drawn refer to the researched cultivar.
Response: Thanks for the suggestion. We have emphasized the researched cultivar in the Conclusion section.
Reviewer 3 Report
The reviewed manuscript is presenting in interesting information supported with a lot of results due to the numerous evaluated parameters. However, it is up to the authors' or editor discretion whether all the results have to be included in the paper, because the results section is quite rich, in my opinion at the expense of the Introduction and Discussion sections, which could be a bit longer. In addition, the results are already divided and commented in the paper itself and also in the supplementary data, which I think is not ideal. I see the supplementary data as an opportunity to supplement (not divide) the results included in the paper - for example, describing results from individual years of long-term experiment in the supplement, while in the paper I describe average multi-year results.
I have several comments to the presented manuscript:
1. In abstract, it should be mentioned that it was two years field experiment. This is only apparent from the Methodology chapter. In the current version of the abstract, the experiment appears to be a one-year field experiment, which is not good.
2. In abstract, kg N ha−1 is not an SI unit in my opinion. It should be kg ha-1 N (of N)
3. Introduction chapter - I think that the question of irrigation (especially AWD) could have been discussed a bit more, as it is the point of the article. As I mentioned above, the scope of the article is affected by the large amount of data (discussed in article and even in supplementary data). This comment can also be related to the Discussion chapter.
4. Methodology chapter - I recommend adding BBCH for all vegetation stages discussed in the paper and explained only via shortcuts.
5. Methodology chapter – shortcuts JT, HD, MA are not explained anywhere, unless I missed it.
6. Results chapter - Figures should be the same everywhere - somewhere the legend is on the right, somewhere it is missing, somewhere it is classically near the axis - I understand that these are linked graphs, but even in this case they should be properly labelled. Or at least have everything correctly described in graph A (top left) - in the current version it is graph C, sometimes D, ...
7. Results + Discussion + Methodology chapter - There are too many abbreviations in the article for a person outside the experiment - it is necessary to keep tracking down what is what. At least for the vegetation phases (MT, PI, ...) I recommend using BBCH as mentioned before (or at least always put the BBCH in brackets). I would use abbreviations only for irrigation regimes, I think nitrogen rates can be described by numbers (120 kg/ha, 240 kg/ha and 360 kg/ha) instead of abbreviations.
8. I think the article presents an interesting result. Unfortunately, I find the large amount of data and the large number of abbreviations overwhelming in current state, so for now I rate the interest to the readers and overall merits as low, but I believe it can be improved.
Author Response
Reviewer 3
Comments and Suggestions for Authors
The reviewed manuscript is presenting in interesting information supported with a lot of results due to the numerous evaluated parameters. However, it is up to the authors' or editor discretion whether all the results have to be included in the paper, because the results section is quite rich, in my opinion at the expense of the Introduction and Discussion sections, which could be a bit longer. In addition, the results are already divided and commented in the paper itself and also in the supplementary data, which I think is not ideal. I see the supplementary data as an opportunity to supplement (not divide) the results included in the paper - for example, describing results from individual years of long-term experiment in the supplement, while in the paper I describe average multi-year results.
Response: Thanks for the suggestion. We have expanded the content in the discussion section and analyzed the possible underlying reasons for the differences observed in the positive and negative responses resulting from irrigation regimes and N application rates (lines 434-465). Furthermore, we have also examined the potential reasons for the variations in water use efficiency (WUE) and highlighted and reflected upon the limitations of the experimental design in this study (lines 404-419 and lines 456-466).
Due to the extensive data obtained in this study, we have chosen to include only the key data in the manuscript for the conciseness. The remaining data has been included in the supplementary materials. It is important to note that the supplementary materials do not serve as additional explanations or interpretations for specific data or results.
I have several comments to the presented manuscript:
- In abstract, it should be mentioned that it was two years field experiment. This is only apparent from the Methodology chapter. In the current version of the abstract, the experiment appears to be a one-year field experiment, which is not good.
Response: Thanks for the suggestion. We have added the year in the Abstract section.
2 In abstract, kg N ha−1 is not an SI unit in my opinion. It should be kg ha-1 N (of N)
Response: Thanks for the suggestion. We have corrected it.
- Introduction chapter - I think that the question of irrigation (especially AWD) could have been discussed a bit more, as it is the point of the article. As I mentioned above, the scope of the article is affected by the large amount of data (discussed in article and even in supplementary data). This comment can also be related to the Discussion chapter.
Response: Thanks for the suggestion. We have provided additional discussion on the aspects related to AWD in the Discussion section (line 404-419 and line 434-455).
- Methodology chapter - I recommend adding BBCH for all vegetation stages discussed in the paper and explained only via shortcuts.
Response: Thanks for the suggestion. In my personal opinion, BBCH is a widely used method internationally for dividing crop growth stages, but the numbering of the stages varies across different classification standards. In China rice production, using specific growth stage names would obviously be more intuitive, and we have added the number of days after transplanting corresponding to each growth stage in the M&M section (line 123 and line 134-136). We have also included an abbreviation section at the end of the manuscript to facilitate reader’s comprehension.
- Methodology chapter - shortcuts JT, HD, MA are not explained anywhere, unless I missed it.
Response: We have included an abbreviation section at the end of the manuscript to facilitate reader comprehension (line 502-512) and also explained below the figures.
- Results chapter - Figures should be the same everywhere - somewhere the legend is on the right, somewhere it is missing, somewhere it is classically near the axis - I understand that these are linked graphs, but even in this case they should be properly labelled. Or at least have everything correctly described in graph A (top left) - in the current version it is graph C, sometimes D, ...
Response: Thanks for the suggestion. We have standardized the format of all legends in the figures.
- Results + Discussion + Methodology chapter - There are too many abbreviations in the article for a person outside the experiment - it is necessary to keep tracking down what is what. At least for the vegetation phases (MT, PI, ...) I recommend using BBCH as mentioned before (or at least always put the BBCH in brackets). I would use abbreviations only for irrigation regimes, I think nitrogen rates can be described by numbers (120 kg/ha, 240 kg/ha and 360 kg/ha) instead of abbreviations.
Response: We have added explanation for abbreviations below all the figures and tables to facilitate reader understanding regarding the abbreviations of N treatments. Additionally, we have included an abbreviation section at the end of the manuscript (line 502-512).
- I think the article presents an interesting result. Unfortunately, I find the large amount of data and the large number of abbreviations overwhelming in current state, so for now I rate the interest to the readers and overall merits as low, but I believe it can be improved.
Response: We have added explanation for abbreviations below all the figures and tables to facilitate readers understanding. Additionally, we have included an abbreviation section at the end of the manuscript (line 502-512).
Reviewer 4 Report
The article presents rice cultivation with water deficit and N doses. The article is well written, and brings a lot of useful information to rice cultivation. The authors present data and a discussion that provides concrete insights into the use of technologies for rice cultivation and monitoring. The conclusions are adequate. The methodology is well described. There is nothing to comment on in the text of this article.
Author Response
Thanks for your kind suggestion, we are pleased that the paper is a better shape and more convinced now.
Round 2
Reviewer 3 Report
Dear authors,
thank you for the corrections made within the article. I recommend this version to the publication.
